Management of Soil-borne Plant Parasitic Nematodes for Sustainable Production of Field Grown Tomatoes and Cucumbers by Cover Cropping

Final Report for SW97-001

Project Type: Research and Education
Funds awarded in 1997: $21,900.00
Projected End Date: 12/31/2001
Matching Non-Federal Funds: $10,500.00
Region: Western
State: Hawaii
Principal Investigator:
John McHugh
Waikele Farms
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Project Information

Abstract:

[Note to online version: The report for this project includes tables that could not be included here. The regional SARE office will mail a hard copy of the entire report at your request. Just contact Western SARE at 435-797-2257 or wsare@ext.usu.edu.]

A field study was conducted to evaluate the effectiveness of cover cropping as a sustainable pest management tool for root knot and reniform nematode control in commercial vine ripe tomatoes. Treatments were Bare Ground Fallow (6 month fallow), soil fumigation with Metam Sodium (industry standard) and two cover crops: Sunn Hemp (Crotolaria juncea) and Yellow Mustard (Sinapsis alba). Cost effectiveness of all treatments was also examined. The experiment was conducted twice. The first test was completed on October 31, 2000, the second test finished on August 31, 2001. Root knot nematode levels were low in the first iteration of the study so all plots were inoculated with root knot nematode contaminated soil for the second trial. There were no statistically significant yield differences between treatments in the first or second iterations of the trial. Though not statistically significant, tomato yields were consistently higher in Sunn Hemp plots compared to Yellow Mustard and Bare Ground Fallow during both study periods (10 – 30% higher). Root knot and reniform nematode infestation was high during the second trial period but no statistically significant effect of cover cropping on root knot nematode reduction was detected although numbers for both species of nematodes were lowest in Yellow Mustard and Sunn Hemp in the trial ending August 31, 2001. The effect of the number of root knot nematodes on yield was statistically significant and yield generally declined as root knot nematodes increased. The best dollar return per acre was Sunn Hemp with a gross margin of $11,787.88 compared to the industry standard treatment of Metam Sodium soil fumigation at $10,926.94. Information regarding this research was disseminated to the community (ag and general community) by publicized field days (television, radio, print media, and University of Hawaii Cooperative Extension Service) held on January 6, 2001 and June 30, 2001.

Project Objectives:

1. Determine the effectiveness of selected cover crops in reducing and/or controlling plant parasitic nematodes in commercial tomato fields.
2. Determine the economic feasibility of using this control tactic within an existing tomato farming operation.
3. Share the information obtained with tomato growers in the state via University of Hawaii extension personnel and publications.

Research

Research results and discussion:

1. Determine the effectiveness of selected cover crops in reducing and/or controlling plant parasitic nematodes in commercial tomato fields.

A field experiment was conducted at North Shore Farms (a commercial tomato farm) in Waialua on the island of Oahu. The experiment was repeated in 2000 and 2001. Treatments were Bare Ground Fallow (6 months fallow), soil fumigation with Metam Sodium, and two cover crops with known root knot nematode reducing characteristics: Sunn Hemp (Crotolaria juncea) and Yellow Mustard (Sinapsis alba). Experimental design was a randomized complete block with 3 replications per treatment. Plot size was double row, 60 feet long, 5 feet apart. Windbreaks of sudex grass separated every two plots. Data rows were the innermost of each plot (furthest from windbreak). All plots were prepared well in advance of tomato planting. Cover crops were seeded, allowed to grow approximately 3 feet high and then plowed in to plots for decomposition prior to planting tomatoes. Bare Ground Fallow plots were maintained dry and weed free for six months before tomatoes were planted. Metam Sodium plots were maintained in a weedy state until all plots were covered with plastic mulch for tomato production. After beds were prepared for tomatoes (soil preparation, plastic mulch, drip irrigation installed) Metam Sodium was injected into the test plots 17 days before tomato transplant. Preplant weed control was with Gramoxone Extra at labeled rates. After transplant all cropping practices (nutrition, irrigation, pest management) were the same for all treatments. Tomato cultivar used in this study was Merced, a determinate, concentrated fruit set variety. The first iteration of the trial was completed on October 31, 2000, the second on August 31, 2001. Because of low numbers of root knot nematode in 2000 all plots were inoculated with root knot nematode infested soil at the time cover crops were planted for the 2001 test (November 18, 2000) at a rate of 9 quarts of infested soil per plot. Nematode inoculated plots were irrigated immediately to maintain soil moisture necessary for root knot nematode survival.

The effect of nematodes on tomatoes was quantified by examining the effect of cover crop treatments on yield and nematode numbers. Yields for all treatments were relatively good for both runs of the trial (Table 1). Average per acre yield for tomatoes in the U.S. is 28,000 lb. (Knott’s Handbook for Vegetable Growers, 1997). A good yield is 41,000 lb. per acre. Except for the Yellow Mustard treatment all yields were greater than 30,000 lb. per acre for both trial periods. Statistically there were no significant differences between treatments with respect to yield. However, yield was consistently higher in the Sunn Hemp plots when compared with Yellow Mustard and Bare Ground Fallow (10–30% greater in Sunn Hemp). Root knot nematodes were very low in the 2000 trial but much higher in 2001 (Table 2). There were no statistically significant differences between treatments because of high variability between replicates but numbers were lowest in Sunn Hemp and Yellow Mustard plots under high nematode pressure in 2001 (Table 2). Root knot nematode pressure from gall formation was not significantly different in 2000 and 2001 (Table 3). The relationship of number of root knot nematodes to yield was significant at P = 0.10 (Table 4) for the 2001 trial. As number of root knot nematodes increased yield decreased with root knot nematodes accounting for 31.5% of the yield variation (r² = 0.315).

Reniform nematode pressure was high in 2000 and 2001 but no significant differences between treatments were detected (Table 2). The effect of reniform nematode was a reduction in root mass (Table 4). Root mass reduction was significant at P = 0.10 (Table 4) in 2001 with very high reniform nematode pressure. The reduction in root mass accounted for 25.1% of the yield variation (r² = 0.251).

The conclusion of this study is that cover cropping did not significantly influence the impact of nematodes on tomato yield. However, there was no apparent advantage to the industry standard treatment of Metam Sodium for nematode control. Additionally, there was some benefit of Sunn Hemp on production as average yields were highest with that cover crop. The benefits of cover cropping extend beyond the possibilities for nematode management and may contribute in other ways by improving soil organic matter content and serving as green manure. Additionally, the use of cover cropping reduces soil erosion problems associated with a bare ground fallow approach to nematode management and can reduce the need for soil biocide treatments such as Metam Sodium.

2. Determine the economic feasibility of using this control tactic within an existing tomato farming operation.

Results of the economic feasibility of using cover crops in tomato cropping systems in Hawaii are presented in Table 5. The benefits of Sunn Hemp as a cover crop translate into an additional $860.94 gross profit per acre. There were 420 acres of tomatoes grown in Hawaii in 1999 (National Agricultural Statistics Service, October 2000) which translates into a potential $361,594.80 increase in farm value.

3. Share the information obtained with tomato growers in the state via University of Hawaii extension personnel and publications.

Information on this project was shared with the ag community and the community at-large throughout the course of the study period by conducting field days on January 6, 2001 and June 30, 2001. Field day notification and dissemination of results was by newspaper (Honolulu Advertiser, North Shore News), radio (KCCN – The Farm Report), television (KITV 4 News), Hawaii Farm Bureau Federation, and the University of Hawaii Cooperative Extension Service. The January 6 field day focused on the cover crops and treatments. Cover crops were in the ground and participants were given handout materials detailing the SARE project and the uses of cover crops. On June 30 the field day centered on the effects of the cover crops on the tomato production. Costs of production and Integrated Pest Management were also discussed. Published reports for the SARE project are planned for the Hawaii Agricultural Research Center Annual Report (distributed to farmers and agencies statewide) and an article for the trade journal Agriculture Hawaii. Additionally, information and experience generated from this project are being leveraged to request funding for additional cover crop projects with the Hawaii Department of Health under the Environmental Protection Agency, Section 319, Clean Water Act. Grant proposal being submitted by the Hawaii Farm Bureau Federation.

Research conclusions:

The benefits of cover cropping requires further study. The indications from this project are that while cover cropping may not reduce nematode populations and pressure there is no apparent benefit from the use of soil fumigants and/or biocides. Additionally, the use of cover crops can provide a means of controlling erosion by rain or wind in a cropping system where bare ground fallow is the practice while, at the same time, restoring soil organic matter in the form of green manure. The addition of leguminous organic material apparently has some beneficial effect on tomato production and results in a higher dollar return per acre when compared with the industry standards of soil fumigation and bare ground fallow.

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

Dissemination of findings was an objective of this project and is detailed in item #3 of the above section on Specific Results.

Project Outcomes

Project outcomes:

Farmer Adoption

Throughout the course of this project we have sought to interact directly with growers in a capacity that extended beyond the reach of the SARE project. Funding from the American Farmland Trust allowed us to work with the growers to train them in Integrated Pest Management (IPM) techniques which coincided with the SARE project. Cover cropping was presented as a means of managing soil fertility, erosion, and pest problems without the use of pesticides. The use of cover cropping with Sunn Hemp in tomatoes would replace approximately 12,600 gallons of Metam Sodium used per year in Hawaiian cropping systems. Cover crops also present an opportunity to break the cycle of some diseases and pests on small farms where land is limited and chemical use is not desired. The additional per acre dollar return is enticing to the growers who seek to optimize production. The establishment of cover crops for the farmers would also be relatively easy in that seed could be spread, lightly harrowed into the fields and irrigated without much additional input.

Reactions from Farmers and Ranchers

Small growers with fixed acreage (<20 acres) that is intensively cultivated are very interested in this approach to soil revitalization. Many Hawaii farmers produce 3 crops on the same ground throughout the course of a year. Those farmers facing this situation are in need of alternative cropping practices which can restore the vitality of their soil. The challenge is determining the right type of cover crop for the growers soil type and location. In Hawaii the variation in soil conditions is very high so that more site specific trials need to be conducted to determine appropriate cover crops for particular growing areas. Producer Involvement The producer in the project is North Shore Farms owned by Steve and Jeanne Vana. North Shore Farms has provided the field study site, all production inputs, and cooperation and assistance with project data collection. Farmer education: January 6, 2001 Field Day: 48 farmers
Waialua, Oahu

Hawaii Agriculture 2001: 32 participants
January 26, 2001
Hilo, Hawaii

June 30, 2001 Field Day: 46 farmers
Waialua, Oahu

Recommendations:

Areas needing additional study

There is an apparent beneficial effect of Sunn Hemp on tomato yield. Additionally, there are other benefits of cover cropping which were not evaluated such as green manure and reduction of erosion by wind and rain. We are also interested in the use of cover crops to reduce nitrate and phosphate following crops with heavy nutrient application. These areas will become more of a concern as the state of Hawaii struggles to comply with federal Clean Water Act requirements to reduce nitrate and phosphate runoff from agriculture into water bodies. Hawaii’s agriculture landscape has changed dramatically over the last seven years with many intensive, short term, row crops replacing long term plantation agricultural crops such as sugarcane and pineapple. Appropriate nutrient management technology will be required to maintain the viability of these new diversified agriculture endeavors. We feel that cover cropping will play a vital role in supporting the sustainability of new agriculture in Hawaii.

Information Products

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.